US20140104792A1 - Devices Having Flexible Printed Circuits With Bent Stiffeners - Google Patents

Abstract

A flexible printed circuit may be laminated to a metal stiffener. The stiffener may be bent to hold the flexible printed circuit in a desired position. Openings may be formed in the stiffener. Metal traces on the flexible printed circuit may be accessed through the openings. Test points in the metal traces may be accessed through the openings or components may be mounted to the metal traces on the flexible printed circuit through the openings. The stiffener may have bends. The bends may be used to shape the stiffener and flexible printed circuit to form an enclosure. The openings in the stiffener may overlap the bends or may be located away from the bends. Flexible printed circuits mounted on bent stiffeners may be used to form elongated tubes with planar sides.

Description

BACKGROUND
• This relates generally to electronic devices and, more particularly, to electronic devices with flexible printed circuit structures.
• Electronic devices often include printed circuits. Rigid printed circuits are formed from materials such as fiberglass-filled epoxy that are inflexible. Flexible printed circuits are formed from layers of polyimide or other sheets of flexible polymer. Integrated circuits, sensors, cameras, and other components may be mounted to pattered metal traces on rigid and flexible printed circuits.
• In some device configurations, it can be difficult or impossible to mount components within a device housing rigid printed circuits. Flexible printed circuits can be used to address these challenging mounting conditions. Flexible printed circuits may, however, offer insufficient mounting stability. If care is not taken, a component that is mounted to a flexible printed circuit in an electronic device may move during use of the device by a user. This may cause damage to the component and may give rise to reliability issues.
• It would therefore be desirable to be able to provide improved arrangements for mounting components in electronic devices using flexible printed circuits.
SUMMARY
• A flexible printed circuit may be formed from a flexible sheet of polymer such as a layer of polyimide. Metal traces may be formed in the flexible printed circuit. The flexible printed circuit may be laminated to a metal stiffener such as a sheet of stainless steel or other metal.
• The stiffener may be bent to hold the flexible printed circuit in a desired position. Openings may be formed in the stiffener. Metal traces on the flexible printed circuit may be accessed through the openings. For example, test points may be accessed through the openings and components may be mounted to the flexible printed circuit through the openings.
• The stiffener may be used to form a mounting bracket for a component in an electronic device. Screws or other fasteners may be used to mount the stiffener within a device housing and may be used to mount components to the stiffener.
• The stiffener may have bends. The bends may be used to shape the stiffener and flexible printed circuit to form an enclosure. Integrated circuits or other components may be mounted in the enclosure. Components may also be mounted to exterior portions of the enclosure. The openings in the stiffener may overlap the bends or may be located so as to be formed on a planar portion of the flexible printed circuit.
• Flexible printed circuits mounted on bent stiffeners may be used to form elongated tubes with planar sides. Flexible printed circuits may be mounted on one or both sides of a sheet metal stiffener. Elongated tube-shaped flexible printed circuits with stiffeners may be mounted within housing enclosures such as clutch barrel enclosures in a laptop computer.
• Further features, their nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of an illustrative electronic device such as a laptop computer with flexible printed circuit component mounting structures in accordance with an embodiment.
• FIG. 2 is a perspective view of an illustrative electronic device such as a handheld electronic device with flexible printed circuit component mounting structures in accordance with an embodiment.
• FIG. 3 is a perspective view of an illustrative electronic device such as a tablet computer with flexible printed circuit component mounting structures in accordance with an embodiment.
• FIG. 4 is a perspective view of an illustrative electronic device such as a computer display with flexible printed circuit component mounting structures in accordance with an embodiment.
• FIG. 5 a schematic diagram of an illustrative electronic device of the type that may be provided with flexible printed circuit component mounting structures in accordance with an embodiment.
• FIG. 6 is a cross-sectional side view of an illustrative electronic device having flexible printed circuit component mounting structures in accordance with an embodiment.
• FIG. 7 is a diagram of an illustrative system being used to form an electronic device having components mounted using a flexible printed circuit with a stiffener in accordance with an embodiment.
• FIG. 8A is a front perspective view of an illustrative flexible printed circuit with a bent stiffener in accordance with an embodiment.
• FIG. 8B is a rear perspective view of the illustrative flexible printed circuit with the bent stiffener ofFIG. 8A in accordance with an embodiment.
• FIG. 9 is a perspective view of an illustrative flexible printed circuit having a stiffener that is bent along a bend axis that does not overlap an opening in the stiffener in accordance with an embodiment.
• FIG. 10 is a cross-sectional side view of a flexible printed circuit with a stiffener that has been coupled to device structures in accordance with an embodiment.
• FIG. 11 is a cross-sectional side view of a flexible printed circuit with a stiffener that has been coupled to device structures and that has a connector for coupling the flexible printed circuit to other structures in accordance with an embodiment.
• FIG. 12 is a perspective view of an illustrative flexible printed circuit with a bent stiffener that has been used to form an elongated hollow tube having a triangular cross-sectional shape and having components mounted on an exterior surface in accordance with an embodiment.
• FIG. 13 is a perspective view of an illustrative flexible printed circuit with a bent stiffener that has been used to form an elongated hollow tube having a triangular cross-sectional shape and having components mounted on an interior surface in accordance with an embodiment.
• FIG. 14 is a perspective view of an illustrative flexible printed circuit with a bent stiffener that has been used to form a hollow tube having a rectangular cross-sectional shape in accordance with an embodiment.
• FIG. 15 is a cross-sectional end view of an illustrative flexible printed circuit that has been provided with a bent stiffener to form a tube with a triangular cross-sectional shape and that has been mounted within a cavity in an electronic device structure such as a clutch barrel cover in accordance with an embodiment.
• FIG. 16 is a perspective view of a flexible printed circuit mounted on an unbent stiffener in accordance with an embodiment.
• FIG. 17 is a diagram of the flexible printed circuit and stiffener ofFIG. 16 following the formation of a cube from the flexible printed circuit and stiffener by bending the flexible printed circuit and stiffener in accordance with an embodiment.
• FIG. 18 is a perspective view of a flexible printed circuit mounted on a stiffener in a configuration in which the flexible printed circuit and stiffener have aligned openings to accommodate an electronic device structure such as an electrical component or housing structures in accordance with an embodiment.
• FIG. 19 is a perspective view of a flexible printed circuit mounted on a stiffener so that a portion of the stiffener that has openings is not covered by the flexible printed circuit in accordance with an embodiment.
• FIG. 20 is a perspective view of a flexible printed circuit mounted on a stiffener in a spiral configuration in accordance with an embodiment.
• FIG. 21 is a flow chart of illustrative steps involved in forming an electronic device having one or more flexible printed circuits with bent stiffeners in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION
• Illustrative electronic devices that have flexible printed circuits with stiffeners are shown inFIGS. 1,2,3, and4.
• Electronic device10 ofFIG. 1 has the shape of a laptop computer and hasupper housing12A andlower housing12B with components such askeyboard16 andtouchpad18.Device10 has hinge structures20 (sometimes referred to as a clutch barrel) to allowupper housing12A to rotate indirections22 aboutrotational axis24 relative tolower housing12B.Display14 is mounted inupper housing12A.
• Upper housing12A, which may sometimes referred to as a display housing or lid, is placed in a closed position by rotatingupper housing12A towardslower housing12B aboutrotational axis24.
• FIG. 2 shows an illustrative configuration forelectronic device10 based on a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration fordevice10,housing12 has opposing front and rear surfaces.Display14 is mounted on a front face ofhousing12.Display14 may have an exterior layer that includes openings for components such asbutton26 andspeaker port28.
• In the example ofFIG. 3,electronic device10 is a tablet computer. Inelectronic device10 ofFIG. 3,housing12 has opposing planar front and rear surfaces.Display14 is mounted on the front surface ofhousing12. As shown inFIG. 3,display14 has an external layer with an opening to accommodatebutton26.
• FIG. 4 shows an illustrative configuration forelectronic device10 in whichdevice10 is a computer display or a computer that has been integrated into a computer display. With this type of arrangement,housing12 fordevice10 is mounted on a support structure such asstand27.Display14 is mounted on a front face ofhousing12.
• The electrical devices ofFIGS. 1,2,3, and4 have electrical components mounted on flexible printed circuits with stiffeners. The illustrative configurations fordevice10 that are shown inFIGS. 1,2,3, and4 are merely illustrative. In general,electronic device10 may be a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment.
• Housing12 ofdevice10, which is sometimes referred to as a case, is formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials.Device10 may be formed using a unibody construction in which most or all ofhousing12 is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures).
• Display14 may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors fordisplay14 may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components.
• Display14 fordevice10 includes display pixels formed from liquid crystal display (LCD) components or other suitable image pixel structures.
• A display cover layer may cover the surface ofdisplay14 or a display layer such as a color filter layer or other portion of a display may be used as the outermost (or nearly outermost) layer indisplay14. The outermost display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member.
• A schematic diagram ofdevice10 is shown inFIG. 5. As shown inFIG. 5,electronic device10 includes control circuitry such as storage andprocessing circuitry40. Storage andprocessing circuitry40 includes one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage andprocessing circuitry40 is used in controlling the operation ofdevice10. The processing circuitry may be based on a processor such as a microprocessor and other integrated circuits.
• With one suitable arrangement, storage andprocessing circuitry40 is used to run software ondevice10 such as internet browsing applications, email applications, media playback applications, operating system functions, software for capturing and processing images, software for implementing functions associated with gathering and processing sensor data, etc.
• Input-output circuitry32 is used to allow data to be supplied todevice10 and to allow data to be provided fromdevice10 to external devices.
• Input-output circuitry32 can include wired andwireless communications circuitry34.Communications circuitry34 may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications).
• Input-output circuitry32 ofFIG. 5 includes input-output devices36 such as buttons, joysticks, click wheels, scrolling wheels, a touch screen such asdisplay14, other touch sensors such as track pads or touch-sensor-based buttons, vibrators, audio components such as microphones and speakers, image capture devices such as a camera module having an image sensor and a corresponding lens system, keyboards, status-indicator lights, tone generators, key pads, and other equipment for gathering input from a user or other external source and/or generating output for a user.
• Sensors38 ofFIG. 5 include an ambient light sensor for gathering information on ambient light levels. The ambient light sensor includes one or more semiconductor detectors (e.g., silicon-based detectors) or other light detection circuitry.Sensors38 also include proximity sensor components. The proximity sensor components may include a dedicated proximity sensor and/or a proximity sensor formed from touch sensors (e.g., a portion of the capacitive touch sensor electrodes in a touch sensor array fordisplay14 that are otherwise used in gathering touch input for device10). Proximity sensor components indevice10 can include capacitive proximity sensor components, infrared-light-based proximity sensor components, proximity sensor components based on acoustic signaling schemes, or other proximity sensor equipment.Sensors38 may also include a pressure sensor, a temperature sensor, an accelerometer, a gyroscope, and other circuitry for making measurements of theenvironment surrounding device10.
• It can be challenging to mount electrical components such as the components ofFIG. 5 within an electronic device. To facilitate mounting of components inhousing12 ofdevice10, components may be mounted on a flexible printed circuit.
• A flexible printed circuit has a flexible dielectric substrate formed from a sheet of polyimide or other flexible layer of polymer. A flexible printed circuit also has patterned conductive traces such as one or more layers of patterned metal traces.
• Stiffening structures formed from metal or other materials are used to stiffen the flexible printed circuit. Stiffening structures are attached to the flexible printed circuit using adhesive. Bent stiffening structures allow the flexible printed circuit to fit within the potentially tight confines ofelectronic device10 and other structures.
• A sheet of metal such as a layer of metal having a thickness of 0.1 mm to 0.3 mm or other suitable thickness may be used to stiffen a flexible printed circuit, so illustrative configurations for stiffeners that are formed from sheet metal are sometimes described herein as an example. This is, however, merely illustrative. Flexible printed circuit stiffeners may, in general, be formed from any suitable material.
• FIG. 6 is a cross-sectional side view of an illustrative device showing how a flexible printed circuit with a stiffener can be mounted within the device. As shown inFIG. 6,electronic device10 hashousing12.Display14 is mounted inhousing12.Display14 has a display cover layer such asdisplay cover layer50 and a display module such asdisplay module52.Display cover layer50 is a clear transparent member such as a layer of clear glass or a layer of transparent plastic.Display module52 contains liquid crystal display structures, electrowetting display structures, electrophoretic display structures, organic light-emitting diode display structures, or other display structures.
• Device10 ofFIG. 6 contains printedcircuit board66 and flexible printedcircuit structure58.Components68 are mounted on printedcircuit66. Components such ascomponent54 are mounted on flexible printedcircuit board60. Flexible printedcircuit board60 is stiffened usingbent stiffener62 to form stiffened flexible printedcircuit structures58.
• Components68 and54 may include integrated circuits, sensors, cameras, buttons, and other components (e.g., circuitry such as storage andprocessing circuitry40 and input-output circuitry32 ofFIG. 5). Components such ascomponent54 are mounted on printed circuits such as flexible printedcircuit60. With one illustrative example,component54 is an ambient light sensor, camera module, or other electronic component.Components68 are integrated circuits, circuitry such ascircuitry40 and32 ofFIG. 5, camera module structures, light sensors such as ambient light sensors, proximity sensors, etc. Printedcircuit board66 is preferably a rigid printed circuit board formed from a substrate material such as fiberglass-filled epoxy.Components68 are soldered or otherwise electrically mounted on printedcircuit board66.
• Components such ascomponent64 are mounted in the interior ofdevice10. To avoid interference with internal device structures such ascomponent64, printedcircuit structures58 are provided with one or more bends, as shown by the illustrative right-angle bend ofFIG. 6. As shown inFIG. 6,component54 may be mounted under a portion ofdisplay cover layer50. As an example,component54 may be a camera that receives light56 that is associated with an image throughdisplay cover layer50. Components such ascomponent54 may, in general, be any suitable type of component (e.g., a sensor, integrated circuit, connector, discrete component, light-emitting component, audio device, etc.). The use of a camera in the configuration ofFIG. 6 is merely illustrative.
• Flexible printedcircuit material60 is generally too flexible to independently retain a desired bent shape. However,stiffener62 is formed from a material that is sufficiently stiff to resist unbending forces. For example,stiffener62 can be formed from a sheet of stainless steel or other metal that retains its shape following bending (e.g., a sheet of metal having a thickness of less than 0.4 mm, of 0.05 to 0.35 mm, of 0.15 to 0.25 mm, etc.).
• To retain the shape of bent printedcircuit structures58 ofFIG. 6,stiffener62 is bent at a 90° angle, thereby holding flexible printedcircuit60 in a configuration with a 90° bend. Bent flexible printedcircuit structures58 with bends of other angles may also be used indevice10, if desired.
• Illustrative equipment for forming bent flexible printedcircuit structures58 anddevices10 incorporating bent flexible printedcircuit structures58 is shown inFIG. 7.
• Patterning equipment80 is used to form stiffening structures such asstiffener62.Equipment80 may include lasers, milling bits and other machining bits, dies for patterning metal by stamping, and other equipment for patterning metal sheets. As shown inFIG. 7,equipment80 may be used to form stiffeners such asstiffener62.Stiffener62 may be devoid of openings or may have one or more openings such asopening82.
• Component mounting and flexible printedcircuit patterning equipment70 is used to form patterned flexible printed circuits (e.g., by laser trimming, die cutting, or other cutting techniques) and is used to mount components such ascomponent72.Component72 may be an integrated circuit, a camera, an ambient light sensor or other sensor, other components, etc.Solder74 electrically connects pads incomponent72 to pads76 that are part of metal traces78 on flexible printedcircuit60.
• After forming a patterned flexible printed circuit with optional openings and mounted components such ascomponent72, lamination and bending equipment84 can create bent flexible printedcircuit structures58. Lamination and bending equipment84 may, for example, use adhesive to attach flexible printedcircuit60 tometal stiffener62 and may use a computer-controlled press or other bending tool to bendstiffener62 and flexible printedcircuit60 into a desired shape.
• As shown in the illustrative example ofFIG. 7, bent flexible printedcircuit structures58 can be tested usingtester86.Tester86 includes a testing tool such astesting tool88. Computer-controlledpositioner96 controls the position oftester88.Test head90 has probe pins92 that are configured to mate withtest pads78 in the metal traces on flexible printedcircuit60. Due to the presence of opening82, test pins92contact test pads78 on flexible printedcircuit60 whentester88 andtest head90 are moved indirection94 during testing.
• If testing indicates that flexible printedcircuit structures58 include one or more faults, flexible printedcircuit structures58 can be repaired or discarded. If testing withsystem86 indicates that flexible printedcircuits58 are operating satisfactorily, flexible printedcircuit structures58 and other structures100 (e.g., housing structures, additional components, etc.) may be assembled usingassembly equipment98 to produce finishedelectronic device10.
• FIG. 8A is a front perspective view of illustrative bent flexible printedcircuit structures58. As shown inFIG. 8A, bent flexible printedcircuit structures58 include flexible printedcircuit60 andmetal stiffener62. Stiffener62 and flexible printedcircuit60 are bent at an angle A aroundbend axis102. Angle A may have a value of 10-20°, 10-60°, 5-175°, 30-120°, less than 150°, less than 110°, 90°, 45°, less than 60°, 10-50°, more than 15°, or other suitable angle.
• Opening82 may overlapbend axis102. In configurations in whichopening82 overlaps bendaxis102, the flexibility ofstiffener62 is enhanced. Any suitable number ofopenings82 may overlap bend axis102 (e.g., one or more, two or more, three or more, etc.).
• Stiffener62 ofFIG. 8A has a notch.Notch104 allows flexible printedcircuit tail60B of flexible printedcircuit60 to bend with respect to stiffener62 (i.e.,tail60B may bend out of the plane that includesportion58B ofstiffener62 and flexible printedcircuit60. If desired, one or more notches such asnotch104 may be located at the corners of stiffener62 (e.g., notches may be formed by removing rectangular corner portions of stiffener62).
• Test pads78 are accessible throughopening82 bytest system86. If desired, one or more components such ascomponent105 may be mounted on flexible printedcircuit60 inopening104. Components such ascomponents106 and108 ofFIG. 8B can also be mounted on the rear surface of flexible printedcircuit60.Component108 can be a connector such as a board to board connector.Component106 can be an integrated circuit or other device.
• Tail portion60B of flexible printedcircuit60 hasopenings110. Screws or other fasteners can pass through openings110 (e.g., to attachtail portion60B to a housing structure or other structure). Components such ascomponent112 may be attached to flexible printedcircuit tail60B. As an example,component112 may be an ambient light sensor.
• In the example ofFIG. 9, flexible printedcircuit structures58 have been bent to form a right angle instiffener62 and flexible printedcircuit60 alongbend axis102.Opening116 does not overlapbend axis102, thereby increasing the stiffness ofstiffener62 along the bend.Components114 are formed on flexible printed circuit60 (e.g., on portions of flexible printedcircuit60 above and below bend axis102).
• Bent flexible printedcircuit structures58 can be used to form structural elements ofdevice10 such as mounting brackets or other component support structures. In the illustrative configuration ofFIG. 10, for example, fasteners such asscrews118 are being used to attach flexible printedcircuit structures58 to device structures120 (e.g., internal or external housing structures such as portions of housing12). Components such as component122 (e.g., a connector, camera, etc.) are also attached to flexible printedcircuit structures58 usingscrews118. In this way,structures58 serve as a mounting bracket or support structure forcomponent122 to help mountcomponent122 withindevice10. Components124 (e.g., integrated circuits, sensors, cameras, etc.) are mounted to flexible printedcircuit60 in flexible printedcircuit structures58 using solder. Circular openings or openings of other shapes are formed in flexible printedcircuit60 andstiffener62 to accommodatescrews118.
• Brackets that are formed from flexible printedcircuit structures58 may have any suitable shape. As an example, brackets may be formed from flexible printedcircuit structures58 that have louvers, press-in inserts, gussets, snaps, springs, or other shapes. Brackets may have multiple openings, engagement features that are configured to engage with other brackets or components, mounting ledges for receiving planar members and other structures, slots for receiving protrusions on components or other structures, etc. The illustrative bracket shape formed by flexible printedcircuit structures58 ofFIG. 10 is merely an example. Flexible printed circuit brackets with bent sheet metal structures may have other shapes, if desired.
• In the illustrative configuration ofFIG. 11, printedcircuit board130 has opposing upper and lower surfaces on whichcomponents132 have been mounted. Printedcircuit board130 may be a flexible printed circuit board or a rigid printed circuit board (as examples).Board130 has board-to-board connector128. Board-to-board connector128 mates with a corresponding board-to-board connector such asconnector126 on flexible printedcircuit60 in bent flexible printedcircuit structures58. Components such as component124 (e.g., integrated circuits, cameras, sensors, etc.) are mounted to flexible printedcircuit60.Metal stiffener62 holds bent flexible printedcircuit structures58 in the bent configuration ofFIG. 11. Screws such asscrew118 pass through openings in bent flexible printedcircuit structures58 to attach bent flexible printedcircuit structures58 tohousing structures120.
• FIG. 12 shows how bent flexible printedcircuit structures58 may have multiple bends. In the configuration ofFIG. 12, bent flexible printedcircuit structures58 form an elongated hollow tube. The tubular structures ofFIG. 12 extend alonglongitudinal axis134. There are two bends in bent flexible printedcircuit structures58, so that bent flexible printedcircuit structures58 have a triangular cross-sectional shape with a triangular interior cavity.Components136 are mounted to flexible printedcircuit60 on the exterior surfaces of bent flexible printedcircuit structures58.
• In the configuration ofFIG. 13, flexible printedcircuit60 has been formed on the inner surface of the tube formed bystructures58 andcomponents136 have been mounted on the interior surface ofstructures58.
• FIG. 14 shows how bent flexible printedcircuit structures58 may have a rectangular cross-sectional shape. In the configuration ofFIG. 14, bent flexible printedcircuit structures58 haveinner layer138 and outer layer140.Layers138 and140 are bent to form an elongated hollow tube that extends alonglongitudinal axis134.Layer138 may be a flexible printed circuit and layer140 may be a metal stiffening sheet orlayer138 may be a metal stiffening sheet and layer140 may be a flexible printed circuit.Components142 may be mounted to the flexible printed circuit on the inside or the outside of the tube.
• FIG. 15 is a cross-sectional end view of bent flexible printedcircuit structures58 in a configuration in which bent flexible printedcircuit structures58 form an elongated tube (extending into the page in the orientation ofFIG. 15). Flexible printedcircuit structures58 ofFIG. 15 are surrounded byhousing structures12R.Structures12R may be part ofhousing12 ofFIGS. 1,2,3, and4. For example,housing structures12R may form a clutch barrel cover forclutch barrel20 ofFIG. 1.
• As shown inFIG. 15,stiffener62 has been bent to form a tubular shape (extending into the page in the orientation ofFIG. 15) having a triangular cross-sectional shape. Flexible printedcircuit60 has two portions. Outer portion60-1 covers the outer surface ofstiffener62. Inner portion60-2 covers the inner surface ofstiffener62. This type of two-sided arrangement for flexible printedcircuit60 allowscomponents142 to be mounted on both the interior and opposing exterior surfaces of the tube-shaped bent flexible printedcircuit structures58 formed usingstiffener62.
• FIG. 16 is a perspective view of illustrative flexible printedcircuit structures58 in an unbent configuration. The example ofFIG. 16 shows how flexible printedcircuit structures58 may have an unbent shape that allows flexible printedcircuit structures58 to be bent to form an enclosure such asenclosure58E ofFIG. 17. In the example ofFIGS. 16 and 17, the unbent structures ofFIG. 16 have a layout that is suitable for forming into the cube-shaped bent structures ofFIG. 17. Bent flexible printedcircuit structures58E of other shapes may be formed, if desired.
• Components142 may be mounted on the exterior ofstructures58E (when flexible printedcircuit60 has exterior portions), on the interior ofstructures58E (when flexible printedcircuit60 has interior portions), or on both the interior and exterior ofstructures58E (when flexible printedcircuit60 has exterior portions such as portions60-1 ofFIG. 15 and interior portions such as portions60-2 ofFIG. 15.
• The interior ofstructures58E is hollow, so additional components can be mounted in the interior ofstructures58E (e.g., batteries, etc.), if desired.
• FIG. 18 is a perspective view of illustrative bent flexible printedcircuit structures58 with an opening such asopening150 to accommodate components such ascomponent152.Component152 may be a portion ofhousing12, an electronic component, or other structure indevice10. Opening150 may have a notch shape with an open edge or may have a closed shape such as the rectangular shape ofFIG. 18, a circular shape, a shape with curved edges, a shape with straight edges, or a shape with a combination of straight and curved edges.
• In the illustrative configuration ofFIG. 19,portion156 ofstiffener62 in bent flexible printedcircuit structures58 is uncovered by flexible printedcircuit60. Leavingportion156 ofstiffener62 bare of flexible printed circuit materials allows fasteners and other structures to bear directly againststiffener62 in the vicinity ofopenings154. If desired, flexible printedcircuit60 may have a portion that overhangs the edge ofstiffener62 such asillustrative tail portion60B ofFIGS. 8A and 8B.
• FIG. 20 is a perspective view of bent flexible printedcircuit structures58 in a configuration in which bent flexible printedcircuit structures58 have a spiral shape. Components such ascomponent142 may be mounted on flexible printedcircuit60. Spiral-shapedstiffener62 holds flexible printedcircuit60 in a desired shape such as a shape with a cylindrical shape, as shown inFIG. 20. Flexible printedcircuit structures58 of the type shown inFIG. 20 may have multiple loops (e.g., two or more, five or more, or ten or more) and may be installed within cylindrical portions ofhousing12 or other portions of device10 (as examples).
• Illustrative steps involved in forming electronic devices having bent flexible printedcircuit structures58 are shown inFIG. 21. Atstep200, equipment such aspatterning equipment80 ofFIG. 7forms stiffener62. Openings such asopening82 can be incorporated intostiffener62, if desired.Stiffener62 may be formed from stainless steel, other metals, or other materials that hold shape when bent. Techniques such as stamping, die cutting, machining using a cutting bit, or other fabrication techniques may be used to formstiffener62.
• Atstep202, flexible printedcircuit60 is patterned and populated with components using equipment70 (FIG. 7). Techniques such as soldering, die cutting, laser cutting, metal trace patterning, and other techniques may be used in forming flexible printedcircuit60.
• Atstep204, flexible printedcircuit layer60 may be laminated tostiffener62. Lamination operations may involve the application of a thermally cured adhesive or other adhesive. A heat source such as an oven or heat gun can apply heat to the thermally cured adhesive to facilitate curing. If desired, flexible printedcircuit layer60 may be laminated tostiffener62 before mounting components on flexible printed circuit layer and/or before patterning flexible printedcircuit layer60.
• Atstep206, computer-controlled die presses or other bending equipment may be used to bendstiffener62 and attached flexible printedcircuit60 into a desired bent shape.
• Atstep208, after attaching flexible printedcircuit60 to stiffener62 and bendingstiffener62 and flexible printedcircuit60 into a desired shape to form bent flexible printedcircuit structures58, circuitry onstructures58 is preferably tested using test system86 (FIG. 7). Ifstructures58 fail testing,structures58 can be reworked or discarded. In response to passing testing,structures58 and other structures100 (e.g., device housing structures, additional device components, etc.) can be assembled to form finishedelectronic device10 using assembly equipment98 (FIG. 7).
• The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Claims (26)

What is claimed is:

1. Apparatus, comprising:

a flexible printed circuit; and

a bent sheet metal stiffener laminated to the flexible printed circuit, wherein the bent sheet metal stiffener has an opening that overlaps at least part of the flexible printed circuit.

2. The apparatus defined inclaim 1 wherein the bent sheet metal stiffener is bent along a bend axis and wherein the opening in the bent sheet metal stiffener overlaps the bend axis.

3. The apparatus defined inclaim 1 wherein the bent sheet metal stiffener is bent along a bend axis and wherein the opening in the bent sheet metal stiffener does not overlap the bend axis.

4. The apparatus defined inclaim 1 further comprising test points on the flexible printed circuit that are access through the opening.

5. The apparatus defined inclaim 1 wherein the sheet metal stiffener comprises stainless steel with a thickness of 0.05 to 0.2 mm.

6. The apparatus defined inclaim 1 wherein the bent sheet metal stiffener is configured to form a mounting bracket.

7. The apparatus defined inclaim 6 wherein the mounting bracket has screw holes.

8. The apparatus defined inclaim 1 wherein the bent sheet metal stiffener has at least three bends.

9. The apparatus defined inclaim 1 wherein the bent sheet metal stiffener is configured to form a tube with multiple flat sides.

10. The apparatus defined inclaim 1 wherein the flexible printed circuit has a flexible tail that extends from the bent sheet metal stiffener.

11. The apparatus defined inclaim 10 further comprising at least one component mounted to the flexible tail.

12. The apparatus defined inclaim 1 further comprising an electrical component mounted to the flexible printed circuit through the opening.

13. The apparatus defined inclaim 1 wherein the bent sheet metal stiffener has a notch and wherein the flexible printed circuit has a flexible tail that extends from the bent sheet metal stiffener at the notch.

14. Apparatus, comprising:

a flexible printed circuit formed from a sheet of polymer with metal traces; and

a sheet metal stiffener to which the flexible printed circuit is attached, wherein the sheet metal stiffener has at least one opening and wherein at least some of the metal traces are accessed through the opening.

15. The apparatus defined inclaim 14 further comprising an electronic component mounted to the metal traces in the opening using solder.

16. The apparatus defined inclaim 14 further comprising a board-to-board connector mounted on the flexible printed circuit.

17. Apparatus, comprising:

a flexible printed circuit attached to a sheet metal stiffener, wherein the sheet metal stiffener has a plurality of bends that form an enclosure; and

electrical components mounted within the enclosure.

18. The apparatus defined inclaim 19 wherein the electrical components comprise integrated circuits mounted on a rigid printed circuit board.

19. The apparatus defined inclaim 17 wherein the sheet metal stiffener has opposing first and second surfaces and wherein some of the flexible printed circuit is attached to the first surface and some of the flexible printed circuit is attached to the second surface.

20. A method, comprising:

laminating a sheet metal stiffener to a flexible printed circuit; and

with a tester, receiving test data through test pins from the flexible printed circuit to which the sheet metal stiffener is laminated.

21. The method defined inclaim 20 wherein the flexible printed circuit has test pads, wherein the sheet metal stiffener has an opening, and wherein receiving the test data comprises receiving the test data through the test pins while the test pins contact the test pads through the opening.

22. The method defined inclaim 20 further comprising patterning a notch into the sheet metal stiffener.

23. The method defined inclaim 22 further comprising patterning the flexible printed circuit to form a tail that bends adjacent to the notch in the sheet metal stiffener.

24. The method defined inclaim 23 further comprising forming openings in the tail.

25. The method defined inclaim 20 wherein laminating the sheet metal stiffener comprises attaching the sheet metal stiffener to the flexible printed circuit with thermally cured adhesive.

26. The method defined inclaim 20 further comprising bending the sheet metal stiffener to form an elongated hollow tube shape for the sheet metal stiffener and the flexible printed circuit.

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